Period Symptoms

What period symptoms are and why they happen

Your menstrual cycle is run by a rise and fall of two main hormones, oestrogen and progesterone. In the second half of the cycle, after ovulation, both hormones climb and then drop sharply if you don’t conceive. That hormone drop in the days before your period is what sets off most premenstrual symptoms — it influences mood-related brain chemistry, fluid balance, and how your breasts and gut feel. It’s a normal, expected part of the cycle, not a sign something is wrong.

Once your period actually starts, a second process takes over. To shed its lining, the uterus releases hormone-like substances called prostaglandins, which make the uterine muscle contract. Those contractions are what you feel as cramps, and high prostaglandin levels can also nudge the bowel, which is why some people notice looser stools or nausea on their heaviest days. Blood loss itself adds to the tiredness many people feel. So “period symptoms” really come from two overlapping causes: the hormonal drop before bleeding, and prostaglandins plus blood loss during it.

The common period symptoms

Most people experience some combination of the symptoms below. They vary in strength from cycle to cycle and from person to person, and getting to know your own usual pattern is one of the most useful things you can do.

Cramps

Cramping in the lower abdomen — sometimes spreading to the lower back or thighs — is the symptom most people associate with periods. It’s driven by prostaglandins making the uterus contract, and it tends to be strongest on the first day or two of bleeding before easing off. Mild-to-moderate cramps that respond to heat or simple pain relief are a normal part of menstruation for many people.

Bloating

That puffy, full feeling around your period comes largely from hormone-driven changes in how your body holds onto water and salt. Bloating often peaks just before bleeding starts and settles within the first few days of your period. Clothes feeling a little tighter and the scale ticking up by a pound or two is common and temporary.

Breast tenderness

Sore, heavy, or swollen breasts in the days before your period are a classic premenstrual sign, caused by hormonal shifts affecting breast tissue. The tenderness usually fades once your period arrives. A supportive bra and easing off caffeine help some people, though the effect is individual.

Mood changes and irritability

Feeling more irritable, tearful, anxious, or low in the run-up to your period is extremely common. The pre-period hormone drop affects brain chemicals tied to mood, including serotonin. For most people these mood shifts are noticeable but manageable and lift once bleeding begins. When low mood or anxiety becomes severe enough to disrupt relationships or daily life, that points toward PMDD (more on that below).

Fatigue

Many people feel noticeably more tired before and during their period. Shifting hormones, disrupted sleep, and — during bleeding — the blood loss itself all play a part. Gentle movement, good sleep, and staying hydrated tend to help more than pushing through on empty.

Headaches

Some people get headaches, or find their usual migraines flare, in the window when oestrogen drops just before the period. These “hormonal” headaches often follow a predictable timing each cycle, which can make them easier to anticipate and manage.

Back pain

Lower back ache often travels with cramps, as the same uterine contractions and prostaglandins refer discomfort to the back. It usually mirrors your cramps — strongest early in the period and easing as bleeding lightens.

Food cravings

Cravings for carbohydrates, sugar, or chocolate are a frequent premenstrual experience and are linked to those same dips in mood chemistry and shifting hormones. They’re a normal part of the cycle for many people; balanced meals and steady blood sugar can take the sharp edge off.

Acne

Breakouts around the period — often along the chin and jaw — are driven by the hormonal shifts of the late cycle, which affect how much oil the skin produces. For many people these spots clear up within a week or so as hormone levels settle.

Digestive changes

Prostaglandins don’t only act on the uterus — they can also speed up or irritate the gut, which is why some people get diarrhoea, nausea, or, conversely, constipation around their period. These changes tend to track the heaviest bleeding days and settle as the period winds down.

PMS vs symptoms during your period

It helps to think of two phases. PMS (premenstrual syndrome) covers the symptoms that build up before bleeding — mood swings, bloating, breast tenderness, cravings, and irritability — and then ease once your period starts. They’re mostly tied to the pre-period hormone drop. Symptoms during the period, like cramps and fatigue on the heaviest days, kick in once bleeding has begun and lean more on prostaglandins and blood loss.

In practice the two often blur together into one stretch of feeling off, which is completely normal. If you want help spotting which premenstrual signs are about to show up, our guide to signs your period is coming walks through the early clues, and our piece on PMS vs pregnancy symptoms untangles the overlap when symptoms could point either way.

What’s normal vs what’s not

For most people, period symptoms are uncomfortable but manageable: a few days of cramps, bloating, low mood, and tiredness that respond to rest, heat, and simple pain relief, then fade as the cycle moves on. That’s the normal range, and having a recognisable pattern each month is reassuring rather than worrying.

Some experiences sit outside that typical range and are worth paying attention to:

• Very severe cramps that stop you doing normal activities, don’t respond to over-the-counter pain relief, or keep getting worse over time.
• PMDD (premenstrual dysphoric disorder) — a more intense form of PMS where mood symptoms like depression, anxiety, or irritability become severe enough to disrupt your relationships, work, or wellbeing in the week or two before your period.
• Symptoms that disrupt daily life month after month, so you regularly miss work, school, or plans.
• Very heavy bleeding, bleeding between periods, or pain during sex, which are worth raising even if your cramps feel ordinary.

None of these mean something is necessarily wrong, and all of them are common reasons people see a provider — but they’re signals worth acting on rather than pushing through every cycle. If your cramps come without any bleeding at all, our explainer on cramps but no period covers the most common reasons why.

Practical relief tips

A few simple, low-cost habits help many people take the edge off period symptoms. None of these is a cure, and what works is personal, so it’s worth trying a couple and seeing what suits you:

• Heat. A hot water bottle or heat pad on the lower abdomen or back is one of the most reliable ways to ease cramps — warmth helps the uterine muscle relax.
• Movement. Gentle exercise like walking, stretching, or light yoga can loosen tension and lift mood, even when resting feels more tempting.
• Over-the-counter pain relief. Anti-inflammatory pain relievers can help with cramps by targeting prostaglandins; always follow the packet instructions and check with a pharmacist if you’re unsure whether they’re right for you.
• Hydration. Drinking enough water can ease bloating and headaches, and cutting back a little on salt and caffeine helps some people.
• Sleep. Period fatigue is real — prioritising rest and a steady sleep routine makes the rest of your symptoms easier to cope with.

Tracking when symptoms tend to land also helps you plan around them. Our Period Calculator estimates when your next period is due, so you can see the symptom-prone days coming and get your heat pad and rest ready in advance.

When to see a provider

Most period symptoms don’t need medical attention — but some patterns are worth raising with a healthcare provider. Consider booking a chat if your symptoms regularly stop you from getting on with daily life; if cramps are severe, don’t ease with usual pain relief, or are getting worse over time; if your bleeding is very heavy or you bleed between periods; if pre-period mood symptoms feel overwhelming or point toward PMDD; or if anything about your cycle changes suddenly and you’re not sure why. A provider can help you understand what’s behind your symptoms and talk through options for managing them.